HIS Paper Research Articles

A highly integrated sensing paper for wearable electrochemical sweat analysis

Wearable electrochemical sensors have attracted tremendous attention in recent years. Significant progress has been achieved, particularly in device integration. Most wearable devices are integrated on thin-film polymer, however, less attention is paid to the sweat flow at human-device interfaces, which is of great significance for continuous real-time analysis and long-term skin comfort. Here, we reported a low-cost, freestanding and disposable highly integrated sensing paper (HIS paper) for real-time analysis of sweat. By using a simple printing process, the HIS paper combining hydrophobic protecting wax, conducting electrodes, and the incorporated MXene/methylene blue (Ti3C2Tx/MB) active materials was assembled. In particular, the printed paper was folded into a multi-layer structure, in which a reasonable designed three-dimensional (3D) sweat diffusion path is established by connecting the hydrophilic regions of each layer, providing efficient pathways for the collection and diffusion of sweat along the vertical direction of the folded HIS paper. More importantly, the independent 3D position of three-electrode facilitates the decoration and fixation of enzymes, as well as the accessibility of electrolytes. In addition, a dual-channel electrochemical sensor that can simultaneously detect glucose and lactate with sensitivity of 2.4 nA μM−1 and 0.49 μA mM−1 respectively was produced based on the HIS paper. This HIS paper provides a miniaturized, low-cost and flexible solution for a range of biochemical platforms, including wearable bioelectronics.

An Ecosophical Inquiry into Digital Mediation and Design in Relation to Alternative Food Networks (AFNs) in an ‘Expanded Field’ of ‘Agri-culture’

T HIS paper brings together several fields of inquiry, including agriculture, art, digital media, design and philosophy, to make a tentative, exploratory re-framing of Alternative Food Networks ( AFN s), and so to re-think and catalyse fresh opportunities for investigation in the humanities. In order to understand the ‘now’, 1 we have to begin with the long view of the agricultural story and, critically, the mediation of this story. We need to understand how sequential economic, socio-technical and other factors encouraged paradigmatic shifts in the ways we produce, consume and perceive our food. Since Medieval times farmers and producers have been testing new (alternative) systems of production, variously encouraged or resisted by the dominant socio- technical regime. 2 Reaction to the total dominance of agri-industrial farming in the industrialised, northern, western world nations since the 1950s and now globally led to early experiments in different producer-consumer relations, for example through Community Supported Agriculture ( CSA ) schemes, from the 1980s onwards. 3 During the last twenty years these experiments have multiplied under various monikers, such as sustainable farming, bio-farming, organic farming and AFN s to such an extent that they now represent an ‘expanded field’, to borrow a concept from the art critic Rosalind Krauss. 4 Applying this notion of the expanded field to agriculture leads to a clarification of the terminology and diversity of initiatives that contest intensive agri-industrial farming. Furthermore, it suggests that we are actually exploring a phenomenon of agri-culture, not agriculture, that is the development of farming and food system practices underpinned by new cultural practices and values. 5 Zooming in on the AFNs, which focus on developing new producer-consumer relations, it seems appropriate to consider these developments within Felix Guattari’s ecosophy 6 which he proposed as a means to counter the hegemony of Integrated World Capitalism (IWC), or as we know it today, neo-liberal, global capitalism. So, the key questions raised here are how do the AFNs choose to mediate their activities online, whether they embed an ecosophical approach in doing so, and how these might represent new agriculture. Lastly, I examine the potentiality of design to contribute to amplifying and scaling up AFNs and other practices in ‘an expanded field of agri-culture’.

Understanding the Challenges of Accessing University Support Services: The Perspectives of Staff Members and International Students

International education is a worldwide phenomenon. Many countries host international students as part of their strategic directions to compete and function effectively in an age of globaliz- ation and as a way to advance their knowledge-based economy. Research shows that although inter- national students (IS) bring economic and reported social and cultural benefits, they can experience difficulties when transitioning to university. To help lessen these difficulties, universities and host countries have developed support services to promote successful transition. However research demonstrates that there is a gap between service provision and utilisation, and that although IS need these services, they rarely access them. In this paper we reflect on data from qualitative interviews with a range of international students and university staff in an Australian university (n=73). The data suggests challenges such as perceived language and cultural barriers, unawareness of services, and being uncomfortable as being some of the reasons IS do not access services. It was concluded that specialised services for IS might optimise utilisation. HIS PAPER EXPLORES some of the challenges faced by international students (IS) when accessing support services provided at an Australian university. In this study, IS are defined as on-campus students who hold an international student visa. In Australia, this cohort is typically represented most highly by Chinese (40%); Malay (8%); Indian (7%); Vietnamese (4.5%) and Indonesian (4%) students (AEI, 2011). Presented first is a literature review of the known issues and challenges faced by IS in the context of their utilisation of the numerous services provided by the university. This is fol- lowed by a presentation of a research project constructed around the issues identified in the IS literature. Finally, a discussion around some of the results and findings of the study will be offered, along with some thoughts for future research.

SIMP O<span class="small-caps">perations and the</span> S<span class="small-caps">trange but</span> B<span class="small-caps">eautiful</span> J<span class="small-caps">anus</span>-F<span class="small-caps">aced</span> PC

SIMP OPERATIONS AND THE STRANGE BUT BEAUTIFUL JANUS-FACED PC MICHAEL SICILIANO HIS PAPER EXPLORES some of the logical implications of the use of transposition and inversion operations defined on the set of pcs. Specifically, those operations bring with them a hodgepodge of associated SIMP operations that incompletely and incompatibly describe some, but not all, situations in which some pcs move clockwise around the pc-circle while others move counterclockwise the same number of places. Many of these SIMP operations have been described before, independently of each other, and their musical applications have been explored. I will provide an extensive analysis of passages from Bartók’s Suite, op. 14, to illustrate one set of SIMP operations that has not been previously discussed, and otherwise refer the reader to published analyses that demonstrate the usefulness of the other sets. That analysis will also suggest the desirability of making T 80 Perspectives of New Music these operations compatible, and the impossibility of doing so using just pcs. I will suggest a way of making all these operations compatible, and I will end by illustrating the usefulness of this approach with an analysis. The way of making them compatible does not, of course, arise from a logical implication of inversion of pcs. However, it is strongly suggested by the use of inversion with many musical objects that are not inversionally symmetric, and can perhaps be understood to make the mathematical model of inversion of pcs more accurately reflect the analytic practice of asserting an inversional relation among pcs.1 Because some of the logical implications of inversion become counter-intuitive, I will start by belaboring a simpler system, one with only transpositions. Imagine a passage in which a melody {C, D, E, F} is accompanied by a chord {Eb, F, G, Ab}. I might propose the transformation T3, transposition by three semi-tones clockwise, to describe the relation between the melody and its accompaniment. At this point, I have committed myself to nothing more than the existence of T3. If I wish to add to T3 the idea that operations combine to form other operations, then T3 and this idea of combination commit me to a system that includes T0, T3, T6, and T9. This commitment exists whether the music at hand actually makes use of all four operations. It is worth observing that T3 and the idea of combination do not commit me to the system of twelve Tns, but only to these four of them. Familiarly, the idea of combination and T1 (or T5, T7, or T11) do commit me to all twelve Tns, again, whether or not the music at hand engages all twelve. Say instead that the melody {C, D, E, F} is accompanied by the chord {C#, B, A, G#}, suggesting the transformation I1. I1 and the idea of combination commit me only to I1 and T0 (the identity operation).2 Inversions, of course, are their own inverses, so any inversion (and the idea of combination) commits me only to that inversion and T0. However, inversions combine with transpositions to form other inversions . Therefore, if I am committed to the twelve Tns and to a single In, I am committed to the entire Tn/In group of twelve transpositions and twelve inversions, again, whether or not the music at hand engages all twenty-four transformations. Indeed, accepting any inversion, and just T1 (or T5, T7, or T11) and the idea of combination, commits me to the full group of twelve Tns and twelve Ins.3 So far I have been belaboring simple systems. The next step is less familiar. In being committed to the Tn/In group, I must also be committed to everything logically implied by that group. The group contains many subsets (some of which are sub-groups), and therefore whatever is implied by any of those subsets is also implied by the group that contains them. That is, if I have a group, I thereby also already SIMP Operations 81 have all of its sub-groups, and thereby I also have everything that comes along with those sub-groups. Some of the sub-groups of the Tn/In group do bring baggage along with...

Kinship Terminology and Linguistic Structure

T HIS paper is an attempt to elucidate the relationship of kinship terminology to the rest of linguistic structure. Various anthropologists have shown (e.g. in this volume) that kinship terminologies are neatly structured. They can be described in terms of certain elements and certain relationships among these elements, as can phonological and grammatical systems. But as a kinship terminology is a terminology, it must be part of a language; so these elements must be linguistic elements, and these relationships must be linguistic relationships. Thus their proper description must in some form belong in the overall description of a linguistic structure. To understand fully the nature of kinship systems it is necessary to understand what kind of linguistic elements these are, and what kind of linguistic relationships. Are the relationships found in kinship terminologies (and similar systems) different from those found in other parts of linguistic structure, or not? Where does their description fit in to the overall description of a language? Where do the elements (of various kinds) fit into the overall structure? The answers are not already available, since anthropologists have tended not to work on integrated linguistic theories, and since linguists have not yet done very much systematic work on lexological and semological structures. Moreover, there is not even any general agreement among linguists on what the elements and relationships are among those areas of linguistic structure that have been more intensively investigated, nor on how they may best be described. In this absence of agreement, a structural interpretation of kinship terminology can be valuable for general linguistic theory as well as for social anthropologists, since the data provided by kinship systems (along with various other kinds of data) can serve to separate the men from the boys, i.e. the linguistic theories that can neatly account for them from those that cannot.

Aviation Safety Priorities in Emerging Air Transport Systems

technologic, geographic, or regulatory attributes. This paper also discusses the validity of transferring priorities in aviation safety across industry segments (delineated by these same attributes), each of which may have unique hazard and vulnerability exposures. Collectively, this paper discusses the potential for identified aviation safety priorities (which may be biased toward dominant industry segments) to mask unique hazard and vulnerability exposures inherent in emerging aviation markets. This potential biasing of safety priorities becomes a more critical topic when viewed from the perspective of a future commercial aviation industry with a greater reliance on Part 135 commuter- and air-taxi-type operations using nontowered airports under a high-volume operations paradigm. I. Introduction T HIS paper has two purposes. The first is to demonstrate that priorities in aviation safety can be biased toward specific industry segments that may not be fully representative of other subsets of aviation. The second is to demonstrate that establishing safety priorities based on worldwide operations or specific segments of aviation may not be directly applicable to all subsets that cross regional (national or continental), regulatory (Code of Federal Regulations, or CFR, Title 14 Parts 121 and 135), or technological (jet, turboprop, large aircraft, small aircraft, etc.) boundaries. Specifically, this paper demonstrates that safety priorities in domestic commercial aviation operations have been biased to reflect the accident profile of international commercial operations. A metaanalysis of published safety summaries is used to demonstrate the limitations of any assumption that an accident profile of some subset within a global aviation market is correlated to global aviation in the aggregate. The authors consider this review of real vs perceived domestic commercial aviation safety priorities to be a critical factor in forming the perspective that emerging and nascent aircraft operations and aviation markets, such as high-volume operations (HVO) at nontowered airports and the burgeoning air-taxi industry using light and very light jets (VLJ), may have unique hazard and vulnerability exposures relative to more traditional commercial aviation markets. If these emerging industry sectors are not critically analyzed for sector-specific hazards and vulnerabilities, there is a potentialforincreasednumbersandratesofaccidentsasthesesectors grow. Any such increase could lead to subsequent delays in societal acceptance of HVO in the nontowered “community” airport environments and potential delays in the growth of these emerging aviation markets that would directly affect the capacity of the commercial air transport industry in the aggregate as the hub-andspoke infrastructure nears its maximum capacity. This paper first revisits an earlier work by the authors [1] that critically reviewed aviation accident data summaries compiled and released by various governmental, nongovernmental, and quasigovernmentalorganizations[2–6].Inthispreviouswork,theauthors

Broadening the boundaries of psychology through community psychology

HIS PAPER argues for community psychology to be included within the discipline boundaries of psychology. In doing this, it will enable psychology to begin to address some of the large scale social issues affecting people’s well-being. It will be necessary, however, to incorporate aspects of other disciplines, make explicit the political dimensions of psychological knowledge and practice and adopt an action-oriented more student-centred approach to learning. The paper will draw on student experiences to illustrate the value of community psychology learning. Radford (2008) raised a number of issues challenging the boundaries of the discipline of psychology and the relevance of an education in psychology as overseen by the British Psychological Society. In this paper I will further the case for a psychology that addresses real world issues and goes beyond its current boundaries. In doing this I will explore the extent to which community psychology is contained within the boundary of psychology; the challenges that an emergent community psychology might make to the parent discipline; and the benefits to students of community based learning of community psychology. Discipline boundaries

Control and Simulation of Relative Motion for Aerial Refueling in Racetrack Maneuvers

T HIS paper focuses on the development of an integrated simulation environment and control algorithms for a receiver aircraft in boom–receptacle refueling (BRR) operation while the tanker flies in a racetrack maneuver. A racetrack maneuver is the standard pattern flown by tanker aircraft, with straight legs and bank turns [1]. This paper applies the earlier work by the authors on mathematical modeling of relative motion [2,3] and aerodynamic coupling [4] to the simulation of aerial refueling, and it develops control laws for the motion of the receiver relative to the tanker that flies in racetrack maneuvers. An integrated simulation environment is developed to take into account tanker maneuvers, motion of the receiver relative to the tanker, and the aerodynamic coupling due to the trailingwake vortex of the tanker. The separate dynamicmodel of the tanker, including its own controller, allows the simulation of the standard racetrack maneuvers of the tanker in aerial refueling operations. The mathematical model of the receiver expressed in terms of the relative position and orientation with respect to the tanker’s body frame facilitates the formulation, in a single framework, of maneuver and stationkeeping of the receiver behind the tanker. For the racetrack maneuvers of the tanker, a linear quadratic regulator (LQR)-based multi-input/multi-output (MIMO) state feedback and integral control technique is developed to track commanded speed, altitude, and yaw rate. Similarly, for the relative motion of the receiver, an LQR-based MIMO state feedback and integral control technique is designed to track the commanded trajectory expressed in the body frame of the tanker. Both controllers schedule their corresponding feedback and integral gains based on the commanded speed and yaw rate of the tanker. The tanker aircraft model represents KC-135R, and the receiver aircraft model is a tailless fighter aircraft with innovative control effectors (ICE) and thrust-vectoring capability. Because the receiver has redundant control variables, various control allocation schemes are investigated for trajectory tracking and stationkeeping while the tanker flies in various racetrack maneuvers with different commanded turn rates.

Optimal Path Planning for Unmanned Combat Aerial Vehicles to Defeat Radar Tracking

The problem of path planning for unmanned combat aerial vehicles (UCAVs) in the presence of radar-guided surface-to-air missiles is treated. The problem is formulated in the framework of the interaction between three subsystems: the aircraft, the radar, and the missile. The main features of this integrated model are as follows. The aircraft radar cross section (RCS) depends explicitly on both the aspect and bank angles; hence, the RCS and aircraft dynamics are coupled. The probabilistic nature of radar tracking is accounted for, namely, the probability that the aircraft has been continuously tracked depends on the aircraft RCS and range. Finally, the requirement to maintain tracking before missile launch and during missile flyout are also modeled. Based on this model, the problem of UCAV path planning is formulated as a minimax optimal control problem, with the aircraft lateral acceleration serving as control. Necessary conditions of optimality for this minimax problem are derived and used as a basis for an efficient numerical solution. Illustrative examples are considered that confirm the standard flying tactics of “denying range, aspect, and aim,” by yielding flight paths that weave to avoid long exposures of aspects with large RCS. HIS paper is devoted to the problem of automated path planning for unmanned combat aerial vehicles (UCAVs) in the presence of radar-guided surface-to-air missiles (SAMs). This problem features the interaction between three subsystems: the aircraft and its characteristics, the radar and its capabilities, and the missile and its lethality. Therefore, the solution of the UCAV path-planning problem requires realistic models of these three subsystems. Although the current literature offers models for each of them separately, there is no approach that integrates models of the three subsystems in a unified framework. The purpose of this paper is to propose such an integrated model and present results on its use.

Um aspecto da diversidade cultural do caboclo amazônico: a religião

ESTE TRABALHO trata de um aspecto da diversidade cultural do caboclo amazônico, isto é, a religião. Esta se constitui numa espécie de catolicismo popular, que mantém relações com o xamanismo nativo - a pajelança cabocla -, e que se originou de antigas práticas e crenças dos índios Tupinambás, que habitaram parte da região amazônica no período colonial, bem como de influências portuguesas e africanas.

Augmenting Adaptive Approach to Control of Flexible Systems

This paper describes an approach for augmenting a linear controller design with a neural-network-based adap- tive element. The basic approach involves formulating an architecture for which the associated error equations have a form suitable for applying existing results for adaptive output feedback control of nonlinear systems. The approach is applicable to non-affine, nonlinear systems with both parametric uncertainties and unmodelled dy- namics. The effect of actuator limits are treated using control hedging. The approach is particularly well suited for control of flexible systems subject to limits in control authority. Its effectiveness is tested on a laboratory experiment consisting of a three-disk torsional pendulum system, including control voltage saturation and stiction. HIS paper describes an approach for augmenting a linear con- troller design with a neural-network (NN)-based adaptive el- ement. Previous adaptive output feedback control approaches have been applied within a control architecture that uses an inverting type of controller for the nonadaptive portion of the control system. 1,2 Considering that the vast majority of controllers are locally linear controllers, it would be highly desirable to retrofit such systems with an adaptive element, rather than to replace them with an inverting controller. In particular, within the aircraft and automobile industries there is a legacy of experience with existing control system archi- tectures, and these industries would much prefer to augment their controllers with an adaptive process, rather than replace them with a totally new architecture. This is particularly the case in applications calling for control of flexible systems. Several attempts to develop a method for adding an adaptive ele- ment to an existing controller architecture have recently appeared in the literature. 3−9 The methods 3−6 are restricted to state feedback and impose restrictive conditions with respect to properties of the reg- ulated variable and the manner in which the uncertainty affects the plant. For example, they might require that the regulated output has full relative degree (meaning that the number of times the regulated variable must be differentiated before the control appears equals the number of state variables needed to describe the plant dynamics) or that the plant uncertainty is matched (meaning that the uncertainty enters the plant dynamics in the same manner as the control). Be- cause the methods 3−7 are based on matching the state response of an idealized model with that of the true plant, they cannot be applied to a system of higher order than the model used in the design process. As a consequence, they are not robust to the unmodeled dynam- ics. The methods in Refs. 8 and 9 use an adaptive technique called input error method 10 for reconfigurable flight control. It requires, however, that the open-loop system is stable. State feedback is very restrictive, and flexible systems provide a good example in which a state feedback approach is not useful. The controller architecture proposed in this paper relies on re- cent developments in the area of nonlinear adaptive output feedback

Agent toolkit satisfaction and use in higher education

T HIS PAPER presents results from a recent research investigation on the satisfaction and use of intelligent agent toolkits by instructors in higher education. An adaptation of the Technology Acceptance Model (TAM) linking agent toolkit satisfaction and usage to key characteristics of user considerations, performance, and functionality serves as the study's theoretical framework. Data collection consists of the completion of an online questionnaire by 87 international instructors of agent-related courses. Results indicate that no single uniform toolkit satisfies the needs of instructors. Moreover, findings suggest that satisfaction levels are influenced primarily by user interactions with the toolkit, followed to a lesser extent by toolkit performance and functionality. This has a bearing on the utility of agent toolkits in the classroom as results point to a strong relationship between instructor satisfaction and the continuation of use of agent toolkits in future agent-related courses. Characteristics of an ideal agent toolkit for the classroom are also identified.

Low-Mach-Number Preconditioning Applied to Turbulent Helicopter Fuselage Flowfield Computation

HIS paper deals with the problems encountered in simulating low-Mach-number e ows encountered in applied aerodynamics. Typical examples are e ows over external aerodynamic bodies such as helicopter fuselages, road vehicles, submarines, and multielement airfoils at high angles of attack. Low-speed e ows may be compressible because of surface heat transfer or volumetric heat addition. Classical numerical methods for the simulation of compressible viscous e ows using the Reynolds averaged Navier‐ Stokes (RANS)equationsperformsatisfactorilyinmoste owregimes(from mediumsubsonice owtohypersonice ow).However,inthelowsubsonic e ow regime, that is, for Mach numbers lower than about 0.1, these methods give poor results in terms of convergence rate and solution accuracy. The dife culty in solving the compressible equations for low Mach numbers is associated with the large ratios that exist between the acoustic and convective wave speeds. Two approaches are currently considered to solve this problem. The e rst is a perturbation method. It is based on a perturbed form of the equations where the physical acoustic waves are replaced

Near Eastern Theatres in Late Antiquity

HIS PAPER EXAMINES THE THEATRES AT Bostra, Caesarea, Neapolis (Nablus), and Petra in their final centuries of use, considering in particular their architectural form, their function, and the circumstances of their eventual abandonment. The analysis ties into two lines of investigation into the nature of public spectacles in late antiquity. On the one hand, architectural evidence has suggested to several scholars that theatres were adapted in late antiquity for the production of a wide array of spectacles, including gladiatorial combat, venationes, and aquatic shows.1 On the other hand, the importance of theatrical entertainment in late antique Rome is confirmed by the codex-calendar of A.D. 354, in which 177 days are associated with ludi scaenici and circenses.2 Various literary sources indicate the persistent popularity of festivals and theatrical entertainment in the Near East as well.3 This study offers a re-interpretation of the later form of theatres in the Near East in light of the regional architectural tradition and the strength of the literary testimony.4 The earliest known theatres in the Near East were constructed at the end of the first century B.C. and beginning of the first century A.D., during programs undertaken in Judaea and Nabataea by local kings under the influence of Rome, and in Syria byJulius Caesar and Augustus.5 The number of imperial dedications

Stabilizing Motion Relative to an Unstable Orbit: Applications to Spacecraft Formation Flight

Acontrol lawisderivedandanalyzed thatstabilizesa classof unstableperiodicorbitsin theHillrestrictedthreebody problem. The control law is derived by stabilizing the short-time dynamics of motion about a trajectory by the use of a feedback law specie ed by the instantaneous eigenvalue and eigenvector structure of the trajectory. This law naturally generalizes to a continuous control law along an orbit. By applying the control to an unstable periodic orbit, we can explicitly compute the stability of the control over long periods of time by computing the monodromy matrix of the periodic orbit with its neighborhood modie ed via the control law. For the case of an unstable halo periodic orbit in the Hill restricted three-body problem, we e nd that the entire periodic orbit can be stabilized. The resulting stable periodic orbits have three distinct oscillation modes in their center manifold. We discuss how this control can be applied to formation e ight about a halo orbit. Some practical implementation issues of the control are also considered. We show that the control acceleration can be provided by a low-thrust engine and that the total fuel cost of the control can be quite reasonable. I. Introduction T HIS paper studies the stabilization of an unstable periodic orbit in the Hill problem, which can serve as a general model for motion in the Earth‐ sun system. Results of this study will be relevant to the dynamics and control of a constellation of spacecraft in an unstable orbitalenvironment such as found near the Earth‐ sun libration points. It will also shed light on the practical control and computation of a single spacecraft trajectory in an unstable orbital environment over long time spans. We investigate the application of feedback control laws to stabilize a periodic orbit in the sense of Lyapunov (see Ref. 1) (note, not asymptotic stability). Thus, the stabilized trajectory will consist of oscillatory motions about the nominal trajectory, which in this context can be interpreted as motions in the center manifold of the stabilized periodic orbit. We show that an entire class of such control laws can be dee ned and their stability analyzed as a timeperiodic linear system. The fuel expenditure for such control laws is often quite small and scales with the mean distance between the controlled motion and the nominal trajectory (which is a periodic orbit in this application). The problem of spacecraft control in unstable orbits is not new. (See Refs. 2 and 3 for reviews.) However, these previous studies have focused on stationkeeping control for a single spacecraft and have not considered how the relative motion of a formation of spacecraft could be stabilized and their dynamics modie ed, which is what we consider here. Proposed space observatories of the future include ambitious interferometricimagersthatusebaselinesofhundredsorthousandsof kilometers between spacecraft to attain sufe ciently high resolutions to image planets around distant stars. To carry out these imaging procedures requires that the relative motion between spacecraft be known extremely accurately and that the spacecraft “ e ll in” an effective image e eld as they move relative to each other. A periodic

Numerical Investigation of Transonic Resonance with a Convergent-Divergent Nozzle

At pressure ratios lower than the design value, convergent ‐divergent nozzles often undergo a e ow resonance accompaniedbytheemissionofacoustictones.Thephenomenon,drivenbytheunsteadyshockwithinthedivergent section of the nozzle, has been studied experimentally previously. The space ‐time conservation element solution element method is employed to numerically investigate the phenomenon. The computations are performed for a given nozzle geometry forseveral different pressure ratios. Sustained limit-cycleoscillations are encountered in all cases. The oscillation frequencies and their variation with pressure ratio, including a stage jump, agree well with the experimental results. The unsteady e ow data cone rm that stage 1 of the resonance (fundamental) involves a one-quarter standing wave, whereas stage 2 (third harmonic ) involves a three-quarter standing wave within the divergent section of the nozzle. Details of the shock motion, the e ow, and the near acoustic e eld are documented for one case each of stages 1 and 2. I. Introduction T HIS paper is concerned with an aeroacoustic resonance often encountered with convergent‐ divergent nozzles when run near transonic conditions. The resonance is usually accompanied by the emission of intense acoustic tones. Whereas a casual observer may easily confuse it with the well-known screech tone, it has been shown to be different in character as well as origin. The frequency of the tone increases with increasing plenum pressure. The frequency variation may involve a staging behavior, that is, an abrupt jump in frequency. Whereas odd harmonic stages take place at lower pressures, the fundamental takes place over a wide rangeof higher pressures. Depending on nozzle geometry, the fundamental has been found to persist to pressure ratios as high as 5. The phenomenon has been identie ed and studied experimentally by Zaman etal. 1 For a discussion of background, technological relevance, and pertinent past work from the literature, see Ref. 1. A discussion of numerical works from the literature apparently capturing the same phenomenon, and the implication of those results, will be deferred to the discussion in Sec. V. During the course of the experimental study a numerical study was initiated to complement the investigation. The space‐ time conservation-element and solution-element (CE/SE) method, to be elaborated shortly, was employed because of its past success with e ows involving shocks and acoustic waves. 2 The calculations were e rst performed for a nozzle geometry and pressure ratio that corresponded to an experimental test condition. The result was encouraging in that the e ow not only exhibited a quasi periodicity, but the frequency was also in agreement with the experimental result. Subsequent calculations at two other pressures captured the right trend in the frequency variation as well as the stage jump. These promising results prompted a further study. Thiswas deemedwell-justie ed

Spacecraft Motion About Slowly Rotating Asteroids

Spacecraft motion about an arbitrary second-degree and second-order gravity eeld is investigated. We assume thatthegravityeeldisinuniformrotation aboutanaxisofitsmaximummomentofinertiaandthatitrotatesslowly as compared to the spacecraft orbit period. We derive the averaged Lagrange planetary equations for this system and use them, in conjunction with the Jacobi integral, to give a complete description of orbital motion. We show that, under the averaging assumptions, the problem is completely integrable and can be reduced to quadratures. For the case of no rotation, these quadratures can be expressed in terms of elliptic functions and integrals. For this problem, the orbit plane will experience nutation in addition to the precession that is found for orbital motion about an oblate body. It is possible for the orbit plane to be trapped in a 1:1 resonance with the rotating body, the plane essentially being dragged by the rotating asteroid. As the asteroid rotation rate is increased, this resonant motion disappears for rotation rates greater than a speciec value. Finally, we validate our analysis with numerical integrations of cases of interest, showing that the averaging assumptions apply and give a correct prediction of motion in this system. These results are applicable to understanding spacecraft and particle motion about slowly rotating asteroids. I. Introduction T HIS paper studies the orbital motion of a spacecraft about slowly rotating asteroids. The asteroid gravity e eld is represented by the second-degree and second-order gravity coefecients C20 and C22. The asteroid itself is assumed to be uniformly rotating about the axis of its major moment of inertia. When the asteroid is slowly rotating, we can apply averaging techniques to the Lagrange planetary equations to derive a simplie edset of equations that describe a spacecraft’s orbit. Also, because this is a uniformly rotatinggravitye eld,the Jacobiintegralthatistraditionally used for restricted three-body problems is deened for this problem. 1 Using the Jacobi integral in conjunction with the averaged equations, we can show that the problem can be reduced to quadratures, that is, the problem is integrable. This is an extension of the results that show that the averaged problem is integrable in terms of elliptic, hyperbolic, and trigonometric functions ifthe central body does not rotate. 2 ByproperinterpretationoftheJacobiintegral,wecanderive

Estimating the ignition hazard of 100% cotton clothing worn by transmission and distribution line workers

HIS paper provides technical evaluation criteria for estimating the magnitude of the electric arc current required to ignite 100% cotton fabric worn by transmission and distribution line workers inadvertently exposed to the thermal hazards of an electric arc. This paper is intended to suggest methods for initial evaluation of the ignition hazard assessment of clothing normally worn by transmission and distribution line workers when working on overhead lines operating at 4160 volts, phase to phase, and above. Once the hazard has been identified a further risk analysis is required. The paper does not consider the effects of three-phase arcs, or arcs involving reflected energy, as can be found inside enclosed spaces or equipment. These effects are being studied and may be included when they are quantified. In any event, these types of arcs are not commonly found in overhead work. The paper does not address effects other than electric arcs. An employer’s hazard assessment must take other factors into consideration when determining whether or not 100% cotton clothing is acceptable. ASTM standards provided methods used to test fabrics for ignition and the thermal performance of material. B. Objective

Did Mark Antony Contemplate an Alliance with His Political Enemies in July 44 B. C. E.?

Previous articleNext article No AccessDid Mark Antony Contemplate an Alliance with His Political Enemies in July 44 B. C. E.?John T. RamseyJohn T. Ramsey Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by Classical Philology Volume 96, Number 3Jul., 2001 Article DOIhttps://doi.org/10.1086/449547 Views: 7Total views on this site Copyright 2001 The University of ChicagoPDF download Crossref reports no articles citing this article.

The ‘Commonwealth Effect’ and the Process of Internationalisation

T HIS paper reports the results of a research project, the purpose of which was to assemble the first comprehensive data set on trade and investment relationships within the Commonwealth, and to provide an initial analysis to assess the significance of a ‘Commonwealth effect’ in trade and investment. The empirical results confirmed an overall tendency for high levels of intra-Commonwealth trade and investment, which was not solely explainable by other factors, such as regional trade agreements or geographical proximity. In particular, the ‘discovery’ of a de facto business network is of theoretical interest, as there has been a fair amount of discussion recently concerning the ‘stickiness’ of wealth producing assets, and the competitive advantages arising from the combination of such assets with mobile capital and the ownership-specific advantages of multinational enterprises. Following the decision taken by the Commonwealth in October 1997 to capitalise on its existing network of relationships to foster trade and investment creation, it is pertinent to examine which particular institutional features would account for the observed ‘lumping’ of economic activity within the Commonwealth, whether there is a learning and familiarity effect, and what the relative magnitude of such factors is in comparison to other effects. Towards this purpose, this paper will apply the Swedish internationalisation model of Johanson and